The impedances of electroactive layers with non-uniform resistance and/or capacitance profiles have been simulated using a transmission line model. Simulated data have been compared with experimental data for two types of conducting polymer layer with non-uniform ionic resistance profiles. For a bilayer electrode consisting of a polypyrrole perchlorate inner layer and a more conductive polypyrrole poly(styrene-4-sulphonate) outer layer the experimental impedance data were qualitatively reproduced by a simulation in which two halves of the transmission line have different, but uniform resistances. For poly(3-methylthiophene) films grown at different rotation rates, least-squares fitting of simulations to the experimental impedance data yielded conductivity profiles that increased sharply with distance from the underlying electrode. This is consistent with a previously proposed deposition mechanism in which the concentrations of oligomers build up in solution and then they precipitate in a more porous structure on the electrode. Rotation of the electrode during film growth, to sweep away these oligomers, is shown to result in more uniform and compact films.